Method of lookup table size reduction for depth modelling mode in depth coding

ABSTRACT

A method and apparatus of depth coding using depth modelling mode 1 (DMM1) are disclosed to reduce the wedgelet pattern table size. In one embodiment, a size-reduced wedgelet pattern for a reduced wedgelet pattern table is generated by excluding at least one non-corner adjacent-edge sample for adjacent-edge partition or at least one opposite-edge sample for opposite-edge partition from starting positions or from ending positions. The reduced wedgelet pattern table may also include at least one omitted wedgelet pattern in at least one wedgelet direction category. For the adjacent-edge partition, the starting positions and the ending positions may correspond to every other even non-corner adjacent-edge samples in a first and a second adjacent edges respectively. For the opposite-edge partition, the starting positions correspond to every other even opposite-edge samples in a first opposite edge and the ending positions include all opposite-edge samples in a second opposite edge.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a Divisional of pending U.S. application Ser.No. 15/509,831, filed on Mar. 8, 2017, which is a National Phase of PCTPatent Application No. PCT/CN2015/086469, filed on Aug. 10, 2015, whichis a Continuation-In-Part PCT Patent Application, Serial No.PCT/CN2014/088038, filed on Sep. 30, 2014 and PCT Patent Application,Serial No. PCT/CN2014/088007, filed on Sep. 30, 2014. The PCT PatentApplications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to depth coding in a three-dimensional andmulti-view video coding system. In particular, the present inventionrelates to lookup table size reduction for depth modelling mode 1 (DMM1)in depth coding.

BACKGROUND

High Efficiency Video Coding (HEVC) is a new coding standard that hasbeen developed in recent years. In the High Efficiency Video Coding(HEVC) system, the fixed-size macroblock of H.264/AVC is replaced by aflexible block, named coding unit (CU). Pixels in the CU share the samecoding parameters to improve coding efficiency. A CU may begin with alargest CU (LCU), which is also referred as coded tree unit (CTU) inHEVC. In addition to the concept of coding unit, the concept ofprediction unit (PU) is also introduced in HEVC. Once the splitting ofCU hierarchical tree is done, each leaf CU is further split into one ormore prediction units (PUs) according to prediction type and PUpartition. Several coding tools for screen content coding have beendeveloped. These tools related to the present invention are brieflyreviewed as follow.

Three-dimensional (3D) television has been a technology trend in recentyears that is targeted to bring viewers sensational viewing experience.Multi-view video is a technique to capture and render 3D video. Themulti-view video is typically created by capturing a scene usingmultiple cameras simultaneously, where the multiple cameras are properlylocated so that each camera captures the scene from one viewpoint. Themulti-view video with a large number of video sequences associated withthe views represents a massive amount data. Accordingly, the multi-viewvideo will require a large storage space to store and/or a highbandwidth to transmit. Therefore, multi-view video coding techniqueshave been developed in the field to reduce the required storage spaceand the transmission bandwidth. In three-dimensional and multi-viewcoding systems, the texture data as well as depth data are coded.

Various coding tools have been developed to enhance the depth picturecoding efficiency. Among these tools, the two Depth Modeling Modes (DMM1and DMM4) have been adopted into three-dimensional (3D) video codingstandard such as 3D video coding based on High Efficiency Video Coding(3D-HEVC) to improve the Intra prediction efficiency of depth pictures.DMM1 and DMM4 are based on wedgelet and contour partitioningrespectively. For a wedgelet partition, the two regions are separated bya straight line, as illustrated in FIG. 1A through FIG. 1C, where thetwo regions are labelled with P1 and P2. The separation line isdetermined by a start point S and an end point E, both located ondifferent edges of the block as shown in FIG. 1A, which illustrates acase for the continuous signal and the separation line can be describedby an equation for a straight line. FIG. 1B illustrates a case for thediscrete sample space, where the block consists of an array of sampleswith a block size uB×vB and the start and end points correspond to edgesamples. Though the separation line can be described by a line equationfor the discrete space as well, each boundary sample between regions P1and P2 may not be entirely on one side of the boundary line. Since eachentire sample at the boundary has to be assigned to one of the tworegions, a boundary sample may appear to be on both sides of theboundary line as shown in FIG. 1B. In order to use the wedgelet blockpartitions in the coding process, the partition information is stored inthe form of partition patterns (also referred as wedgelet patterns). Thepartition pattern consists of an array of uB×vB binary data to indicatewhether the sample belongs to region P1 or P2. The regions P1 and P2 arerepresented by black and white samples respectively in FIG. 1C. The term“wedgelet” may also be referred as “wedge” in this disclosure.

Unlike the wedgelets, the separation line between the two regions of acontour partition of a block cannot be easily described by a geometricalfunction. FIG. 2A thought FIG. 2C illustrate examples of contourpartition of a block, where the block consists of two arbitrary shapedregions P1 and P2, and P2 consist of multiple parts. FIG. 2A illustratesan example of arbitrary shaped contour partition for the continuousspace. FIG. 2B illustrates an example of arbitrary shaped contourpartition for the discrete space. Other than separation by a line or anarbitrary shaped contour, wedgelet and contour partitions are verysimilar. In order to use the contour partitions in the coding process,the partition information is also stored in the form of partitionpatterns. FIG. 2C illustrates an example of binary pattern correspondingto the contour partition in FIG. 2B. The binary pattern has to bederived individually for each block from the signal of a referenceblock. Due to the lack of a functional description of the arbitraryshaped contour line between regions, no pattern lookup lists can beused. Consequently no search of the best matching partition can be usedfor contour partitions.

While DMM1 has the advantage of significant BD-Rate savings, the numberof wedgelet patterns for DMM1 requires a large table in both the encoderand the decoder to store the candidate patterns for Intra prediction.The BD-Rate is a well-known performance measure used in video codingsystem. Table 1 lists the size of each wedgelet pattern table for eachIntra PU size in the 3D-HEVC Draft Text 5 (Tech et al., 3D-HEVC DraftText 5, Joint Collaborative Team on 3D Video Coding Extensions of ITU-TSG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 9th Meeting: Sapporo, J P, 3-9Jul. 2014, Document: JCT3V-I1001).

TABLE 1 Number Number of Ac- of bits for one cumu- wedgelet wedgeletTotal lated PU size patterns pattern bits bits Bits ratio [%] 4 × 4   8616  1,376  1,376  0.35%  (1376/396000) 8 × 8   766 64  46,024  50,40011.62%  (46024/396000) >=16 × 16 1,350 256  345,600 396,000 87.27%(345600/396000)

The wedgelet patterns of DMM1 can be classified into six directioncategories (also referred as wedgelet direction categories), as shown inFIG. 3A through FIG. 3F. The six direction categories include fourcorner directions, vertical direction and horizontal direction. Forcorner directions (also referred as adjacent-edge partitions), the edgeline starting positions and ending positions are on two adjacent edgesjoined by the corner sample. For example, the starting positions are inthe edge corresponding to the row of samples at the bottom in FIG. 3A.The ending positions are located in the edge corresponding to the columnof samples at the left in FIG. 3A. For the opposite-edge directions(i.e., vertical and horizontal in FIG. 3C and FIG. 3F respectively), thetwo edges for the starting and ending positions are on the oppositesides. The opposite-edge directions may also referred as opposite-edgepartitions. As shown above, the table size for DMM1 is quite large.Therefore, it is desirable to develop a method to reduce the wedgeletpattern table size. However, reducing the wedgelet pattern table sizemay cause impact on the coding efficiency. Furthermore, it is desirablethat the reduced wedgelet pattern table size will have very small or noimpact on the coding efficiency.

In the current 3D-HEVC described in JCT3V-I1001, the table index in DMM1is binarized as a fixed-length code as described in the syntax table(Table 2) and in the binarization table (Table 3).

TABLE 2 Descriptor if( DepthIntraMode[x0][y0] == INTRA_DEP_DMM_WFULL )    wedge_full_tab_idx[x0 ][y0] ae(v)

TABLE 3 wedge_full_tab_idx FL cMax = wedgeFullTabIdxBits[log2PbSize]

where cMax represents the code bit length of the fixed length code andwedge_full_tab_idx[x0][y0] specifies the index of the wedgelet patternin the corresponding pattern list when DepthIntraMode[x0][y0] is equalto INTRA_DEP_DMM_WFUL.

The wedgelet pattern can be determined according to:wedgePattern=WedgePatternTable[Log2(nTbS)][wedge_full_tab_idx[xTb][yTb]], whereWedgePatternTable[log2BlkSize] represents the list used to store binarypartition patterns for a block with a block size2^(log2BlkSize)×2^(log2BlkSize).

NumWedgePattern[log2BlkSize] specifies the number of binary partitionpatterns in list WedgePatternTable[log2BlkSize].

The wedgelet pattern table WedgePatternTable[log2BlkSize] is constructedaccording to a pre-defined algorithm and the number of wedgelet patternsNumWedgePattern[log2BlkSize] is also determined by this algorithm. Table4 illustrates NumWedgePattern[log2BlkSize] for different log2BlkSize.

TABLE 4 NumWedgePattern log2PbSize 2 3 4 5 6 Value 86 766 1350 1350 —

Table 5 illustrates wedgeFullTabIdxBits[log2Pb Size] for differentlog2BlkSize.

TABLE 5 Initialization variable wedgeFullTabIdxBits log2PbSize 2 3 4 5 6Value 7 10 11 11 13

The terms Log2(nTbS), log2PbSize and log2BlkSize mentioned above havethe same meaning.

A problem occurs for the following case:

-   -   NumWedgePattern[log2BlkSize]<2^(wedgeFullTabIdxBits[log2BlkSize]).

When the above case occurs, the decoder may encounter a bitstream thatsignals a wedge_full_tab_idx larger than or equal toNumWedgePattern[log2BlkSize]. Since WedgePatternTable[log2BlkSize] isconstructed with only NumWedgePattern [log2BlkSize] entries, the accessof WedgePatternTable[log2BlkSize] [wedge_full_tab_idx] withwedge_full_tab_idx>=NumWedgePattern[log2BlkSize] undefined will cause anunpredictable results or an error. Accordingly, it is desirable todevelop a method for wedgelet tables to overcome the issue.

SUMMARY

A method and apparatus of depth coding using depth modelling mode 1(DMM1) for a depth block in a three-dimensional (3D) or multi-view videocoding system are disclosed to reduce the wedgelet pattern table size.In one embodiment, a size-reduced wedgelet pattern for a reducedwedgelet pattern table is generated by excluding at least one non-corneradjacent-edge sample for adjacent-edge partition or at least oneopposite-edge sample for opposite-edge partition from starting positionsor from ending positions. The reduced wedgelet pattern table may alsoinclude at least one omitted wedgelet pattern in at least one wedgeletdirection category. A depth block is then encoded or decoded accordingto the DMM1 mode using the reduced wedgelet pattern table. The depthblock may correspond to a prediction unit (PU).

In one embodiment, for the adjacent-edge partition, the startingpositions and the ending positions correspond to every other evennon-corner adjacent-edge samples in a first adjacent edge and in asecond adjacent edge respectively. For the opposite-edge partition, thestarting positions correspond to every other even opposite-edge samplesin a first opposite edge and the ending positions include allopposite-edge samples in a second opposite edge. In one embodiment, theeven-position samples correspond to edge samples with distances betweenthe selected samples and the same-row-or-column corner point being evennumbers. In another embodiment, the reduced wedgelet pattern tableincluding the size-reduced wedgelet pattern is applied to the depthblock only when the depth block corresponds to a prediction unit with ablock size equal to or larger than 16×16.

The reduced wedgelet pattern table may comprise at least onesize-reduced wedgelet pattern in each wedgelet direction category. Thestarting positions or the ending positions may correspond to every k-thnon-corner adjacent-edge samples with phase t, where k is a positiveinteger and t is a non-negative integer smaller than k. In oneembodiment, at least one non-corner adjacent-edge sample foradjacent-edge partition or at least one opposite-edge sample foropposite-edge partition excluded from the starting positions or from theending positions may depend on a block size of the depth block or awedgelet direction category. For example, at least one non-corneradjacent-edge sample for adjacent-edge partition or at least oneopposite-edge sample for opposite-edge partition is excluded from thestarting positions or from the ending positions only for the block sizeof the depth block equal to or larger than a threshold. The reducedwedgelet pattern table may include at least one omitted wedgelet patternin at least one wedgelet direction category only for a block size of thedepth block equal to or larger than a threshold. Alternatively, at leastone omitted wedgelet pattern can be included only for a block size ofthe depth block smaller than a threshold.

The reduced wedgelet pattern table for a current depth block can be usedas a shared wedgelet pattern table by another depth block having adifferent block size from the current depth block. The table size of thereduced wedgelet pattern table can be pre-defined to a fixed value foreach block size of the depth block, and a required table size associatedwith the number of wedgelet candidates is no larger than the fixed valuefor each block size of the depth block.

In another embodiment, different block sizes may share a same wedgeletpattern table. The wedgelet patterns for a larger block size may bedown-scaled and used by a depth block with a smaller block size.Alternatively, the wedgelet patterns for a smaller block size may beup-scaled and used by a depth block with a larger block size.

In yet another embodiment, an available number of wedgelet patterns forreduced wedgelet pattern table can be determined. The available numberof wedgelet patterns is smaller than a total number of wedgelet patternsincluding all wedgelet patterns for all wedgelet direction categories. Acandidate wedgelet pattern can be added to a current reduced wedgeletpattern table until the current reduced wedgelet pattern table is full.A depth block is then encoded according to DMM1 mode using the lastreduced wedgelet pattern table.

Another aspect of the present invention addresses reconstruction of thewedgelet pattern table for all possible wedgelet pattern indices.According to some embodiments, the wedgelet pattern index is constrainedto a constrained wedgelet pattern index to always point to a valid entryin a wedgelet pattern table. A wedgelet pattern is then retrieved fromthe wedgelet pattern table using the constrained wedgelet pattern indexand the current depth block is decoded according to DMM1 mode using thewedgelet pattern retrieved. For example, the wedgelet pattern index canbe clipped to less than the total number of wedgelet patterns. Inanother example, the wedgelet pattern index can be clipped to a rangefrom zero to a total number of wedgelet patterns minus one. Furthermore,the wedgelet pattern index can be constrained to the constrainedwedgelet pattern index by assigning a fixed valid index to theconstrained wedgelet pattern index, or assigning a valid index dependingon the wedgelet pattern index. The wedgelet pattern index can also bedetermined from the video bitstream by parsing a variable length code,where the variable length code is decoded into an index range from zeroto a total number of wedgelet patterns minus one.

In yet another embodiment, all wedgelet pattern table entries areconstructed so that any received wedgelet pattern index will point to avalid wedgelet pattern. For example, for any wedgelet pattern tableentries with index no less than the total number of wedgelet patterns inthe wedgelet pattern table, these wedgelet pattern entries with indicesno less than the total number of wedgelet patterns can be filled withexisting wedgelet pattern entries with an index range from zero to thetotal number of wedgelet patterns minus one or using new wedgeletpattern entries different from existing wedgelet pattern entries withthe index range from zero to the total number of wedgelet patterns minusone. These wedgelet pattern entries with indices no less than the totalnumber of wedgelet patterns can also be filled with a first validwedgelet pattern in the wedgelet pattern table, or a last valid wedgeletpattern in the wedgelet pattern table, or a default wedgelet pattern.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates an example of wedgelet partition corresponding to acase for the continuous signal and the separation line can be describedby an equation for a straight line.

FIG. 1B illustrates an example of wedgelet partition for a case of thediscrete sample space.

FIG. 1C illustrates an example of wedgelet pattern corresponding to thecase in FIG. 1B.

FIG. 2A illustrates an example of contour partition corresponding to acase for the continuous signal.

FIG. 2B illustrates an example of contour partition for a case of thediscrete sample space.

FIG. 2C illustrates an example of contour pattern corresponding to thecase in FIG. 2B.

FIG. 3A-FIG. 3F illustrate examples of starting positions and endingpositions of available wedgelet candidates in various wedgelet directioncategories, where the wedgelet direction category corresponds toadjacent-edge direction (FIG. 3A, FIG. 3B, FIG. 3D and FIG. 3E) andopposite-edge direction (FIG. 3C and FIG. 3F).

FIG. 4A-FIG. 4F illustrate examples of starting positions and endingpositions of available wedgelet candidates in various wedgelet directioncategories for a reduced wedgelet pattern table according to anembodiment of the present invention, where the starting positions andending positions are constrained at even positions and the wedgeletdirection category corresponds to left-bottom corner direction (FIG.4A), bottom-right corner direction (FIG. 4B), vertical direction (FIG.4C), left-up corner direction (FIG. 4D), up-right corner direction (FIG.4E) and horizontal direction (FIG. 4F).

FIG. 5A-FIG. 5B illustrate another embodiment of the present invention,where the wedgelet patterns for corner directions are the same as thosein FIGS. 4A-B and FIGS. 4D-E. For vertical direction (FIG. 5A) andhorizontal direction (FIG. 5B), only the starting positions areconstrained at even positions.

FIG. 6 illustrates an exemplary flowchart for an encoder systemincorporating reduced wedgelet pattern table according to an embodimentof the present invention.

DETAILED DESCRIPTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

In order to reduce the wedgelet pattern table size associated with DMM1(depth modelling mode 1), three types of wedgelet pattern table sizereduction method are disclosed. According to the first-type wedgeletpattern table size reduction, constraints are applied to the starting orending points (also referred as the starting or ending positions) of theavailable wedgelet candidates, or the available wedgelet directioncategories. According to the second-type wedgelet pattern table sizereduction, the starting and ending points of the wedgelets in the tablesare down scaled (also referred as down sampled) for larger PUs(prediction units). The down-scaled wedgelet candidates are used forsmaller Intra PUs. The wedgelet pattern table can also be used by alarger PU by up scaling the wedgelet patterns in the wedgelet patterntable. According to the third-type wedgelet pattern table sizereduction, the total number of available wedgelets is limited to a fixednumber while adding wedgelet pattern into the wedgelet pattern list. Nonew wedgelet pattern is added when the wedgelet list is full.

Accordingly, a first embodiment based on the first-type wedgelet patterntable size reduction is to constrain the starting position (x, y)according to:

$\begin{matrix}{{x\% k\text{==}m},{{where}\mspace{14mu} m\text{<}k},{and}} & (1) \\{{y\% t\text{==}n},{{where}\mspace{14mu} n\text{<}{t.}}} & (2)\end{matrix}$

In the above equations, “%” corresponds to the “modulo” operation and m,n, k and t are positive integers. Equation (1) corresponds to every k-thsamples of the edge samples in the x-direction and m refers to an offset(also referred as phase in this disclosure) in the down-scaled position.When x is divisible by k, m is equal to 0. For example, if k=2 and m=0,every other edge even samples are used in the x-direction. If k=2 andm=1, every other odd samples are used in the x-direction. Similarly,equation (2) corresponds to every t-th edge samples in the y-direction.

A second embodiment based on the first-type wedgelet pattern table sizereduction is to constrain the ending point position (x, y) by x % k==mand y % t==n, where m<k, and n<t. Similar to the case for the startingpositions, the ending positions are constrained to every k-th edgesamples in the x-direction and every t-th edge samples o in they-direction.

A third embodiment based on the first-type wedgelet pattern table sizereduction is to constrain the ending point position (x, y) to be from alimited set of values, such as x<k or y<t, where k is smaller than theblock width and t is smaller than the block height.

The fourth embodiment based on the first-type wedgelet pattern tablesize reduction is to constrain the starting point position (x, y) to befrom a limited set of values, such as x<k or y<t, where k is smallerthan the block width and t is smaller than the block height.

A fifth embodiment based on the first-type wedgelet pattern table sizereduction is to constrain the starting point or ending point only for aselected subset of PU sizes. For example, the first through the fourthembodiments as mentioned above can be applied to PUs larger than aselected size, such as 16×16.

A sixth embodiment based on the first-type wedgelet pattern table sizereduction is to constrain the starting point or ending point to eachwedgelet direction categories among the 6 wedgelet categories. Forexample, FIG. 4A-FIG. 4F illustrate examples of selected wedgeletpattern subset corresponding to FIG. 3A-FIG. 3F respectively, where thecoordinates of the starting and ending points are constrained to be evenvalues. In another embodiment, the starting and ending positions areconstrained to be at even positions on for corner directions as shown inFIGS. 4A-4B and FIGS. 4D-4E. However, for the vertical direction and thehorizontal direction, only the ending positions are constrained to be ateven positions as shown in FIG. 5A and FIG. 5B respectively. In theforegoing embodiments, the circles filled with cross lines represent thecorner samples, and the circles filled with dots represent the samplescorresponding to the starting and ending positions. The starting andending positions constrained to be at even positions correspond to evennon-corner samples, where each even non-corner sample has an even sampledistances from the corner sample.

A seventh embodiment based on the first-type wedgelet pattern table sizereduction is to only utilize the wedgelet patterns from a selectedsubset A of all the wedgelet direction categories. Let L denote size ofA, L is smaller than 6. For example, only the wedgelet patterns from thevertical direction and the horizontal direction will be included intothe wedgelet pattern table.

Any combination of the embodiments based on the first-type wedgeletpattern table size reduction as mentioned above can be used to furtherimprove the coding efficiency.

A first embodiment based on the second-type wedgelet pattern table sizereduction is to re-use the wedgelet pattern tables associated with n1×n1size Intra prediction for n2×n2 size Intra prediction, where n1 and n2are positive integers, and n2 is smaller than n1. In other words, thereis no need to store wedgelet pattern table for n2×n2 size Intraprediction since it can use n1×n1 wedgelet pattern table.

When a smaller size wedgelet pattern table shares (i.e., “re-use”) alarger wedgelet pattern table as mentioned above, the smaller sizewedgelet pattern table can be generated by down scaling the wedgeletpatterns in the table used for the larger Intra PUs. The down-scaledtable is then utilized for the smaller Intra PUs.

According to another embodiment based on the second-type wedgeletpattern table size reduction, when processing a pixel at position (x,y)of a smaller PU with size n×n, the value at position (k×x, k×y) in thewedgelet pattern table of a larger PU with size m×m can be utilized,where k, m and n are positive integers and k is equal to m/n.

Any combination of the embodiments based on the second-type wedgeletpattern table size reduction as mentioned above can be used to furtherimprove the coding efficiency.

One embodiment based on the third-type wedgelet pattern table sizereduction is to constrain total available wedgelet number (or the tablesize) of the k×k Intra PU to be n to the power of 2 (i.e., 2^(n)), wheren is a positive integer. A larger n can be used for larger Intra codedPUs.

When adding one wedgelet pattern into the wedgelet list, the wedgelet isonly added when the corresponding wedgelet list for the current Intra PUis not full (or total wedgelet storage size is not larger than the tablesize).

Another embodiment based on the third-type wedgelet pattern table sizereduction is to only select limited wedgelet patterns for each wedgeletdirection category to make the total wedgelet storage size be smallerthan a pre-defined table size.

Any combination of the embodiments based on the third-type wedgeletpattern table size reduction as mentioned above can be used to furtherimprove the coding efficiency.

Furthermore, any combination of the embodiments based on any combinationof the first-type, the second-type and the third-type wedgelet patterntable size reductions as mentioned above can be used to further improvethe coding efficiency.

As mentioned before, when the condition:wedge_full_tab_idx>=NumWedgePattern[log2BlkSize] occurs, the decoder maynot work properly for wedge_full_tab_idx signaled in the bitstream. Inorder to overcome the issue, various embodiments are disclosed.

In one embodiment, wedge_full_tab_idx signaled in the bit-stream isconstrained to be lower than NumWedgePattern[log2BlkSize]. Ifwedge_full_tab_idx signaled in a bit-stream is not lower thanNumWedgePattern[log2BlkSize], the bit-stream will be considered asinvalid.

In another embodiment, wedge_full_tab_idx is clipped to a valid range toaccess the wedgelet pattern in the wedgelet pattern list. For example, aclipped wedge_full_tab_idx can be used to access the wedgelet pattern:

-   -   wedgePattern=WedgePatternTable[log2BlkSize][clipped_wedge_full_tab_idx]    -   where the clipped wedge_full_tab_idx is derived according to:    -   clipped_wedge_full_tab_idx=Clip3(0,        NumWedgePattern[log2BlkSize]−1, wedge_full_tab_idx[xTb][yTb])

In one embodiment, if wedge_full_tab_idx points to an invalid entry inWedgePatternTable[log2BlkSize], a valid entry inWedgePatternTable[log2BlkSize] will be used instead. The valid entry maycorrespond to a fixed entry in the table, or it may depend onwedge_full_tab_idx. For example, WedgePatternTable[log2BlkSize] [0] isused if wedge_full_tab_idx is larger thanNumWedgePattern[log2BlkSize]−1.

In another embodiment, all entries that may be accessed bywedge_full_tab_idx in WedgePatternTable[log2BlkSize] are constructed.For example, WedgePatternTable[log2BlkSize] is constructed with2^(wedgeFullTabIdxBits[log2BlkSize]) entries, so that wedge_full_tab_idxis valid for any value from 0 to 2^(wedgeFullTabIdxBits[log2BlkSize])−1.

In another embodiment, the entries in WedgePatternTable[log2BlkSize]with indices larger than NumWedgePattern[log2BlkSize]−1 are filled withsome wedgelet patterns. A filled wedgelet patterns can be identical toan existing pattern in WedgePatternTable[log2BlkSize] with the indexlower than NumWedgePattern [log2BlkSize], or it can be a new patternwhich is not in the entries with the index from 0 toNumWedgePattern[log2BlkSize]−1 in WedgePatternTable [log2BlkSize].

Alternatively, all the entries in WedgePatternTable[log2BlkSize] withindices larger than NumWedgePattern[log2BlkSize]−1 can be set to thelast valid pattern in the WedgePatternTable, i.e., WedgePatternTable[NumWedgePattern[log2BlkSize]−1].

All the entries in WedgePatternTable[log2BlkSize] with indices largerthan NumWedgePattern[log2BlkSize]−1 can also be set to the first validpattern in the WedgePatternTable, i.e., WedgePatternTable[0].

In one embodiment, all the entries in WedgePatternTable are firstinitialized to a default wedgelet pattern. The default wedgelet patterncan be partition 2N×N, partition N×2N, or one of AMP partitions.

Alternatively, all the entries in WedgePatternTable[log2BlkSize] withindices larger than NumWedgePattern[log2BlkSize]−1 can be set to adefault pattern. The default pattern can be partition 2N×N, partitionN×2N, or one of AMP partitions.

In one embodiment, the wedge_full_tab_idx in the WedgePatternTable isbinarized as a variable length code with NumWedgePattern[log2BlkSize]entries. Therefore, the decoded wedge_full_tab_idx will be from 0 toNumWedgePattern[log2BlkSize]−1.

FIG. 6 illustrates an exemplary flowchart for an encoder systemincorporating reduced wedgelet pattern table according to an embodimentof the present invention. The system determines one or more startingpositions and one or more ending positions for a size-reduced wedgeletpattern by excluding at least one non-corner adjacent-edge sample foradjacent-edge partition or at least one opposite-edge sample foropposite-edge partition from said one or more starting positions or fromsaid one or more ending positions in step 610. The size-reduced wedgeletpattern is generated according to said one or more starting positionsand said one or more ending positions in step 620. A depth block isencoded according to DMM1 mode using a reduced wedgelet pattern tableincluding the size-reduced wedgelet pattern in step 630. A flowchart forthe decoder side can be derived similarly.

The above description is presented to enable a person of ordinary skillin the art to practice the present invention as provided in the contextof a particular application and its requirement. Various modificationsto the described embodiments will be apparent to those with skill in theart, and the general principles defined herein may be applied to otherembodiments. Therefore, the present invention is not intended to belimited to the particular embodiments shown and described, but is to beaccorded the widest scope consistent with the principles and novelfeatures herein disclosed. In the above detailed description, variousspecific details are illustrated in order to provide a thoroughunderstanding of the present invention. Nevertheless, it will beunderstood by those skilled in the art that the present invention may bepracticed.

Embodiment of the present invention as described above may beimplemented in various hardware, software codes, or a combination ofboth. For example, an embodiment of the present invention can be acircuit integrated into a video compression chip or program codeintegrated into video compression software to perform the processingdescribed herein. An embodiment of the present invention may also beprogram code to be executed on a Digital Signal Processor (DSP) toperform the processing described herein. The invention may also involvea number of functions to be performed by a computer processor, a digitalsignal processor, a microprocessor, or field programmable gate array(FPGA). These processors can be configured to perform particular tasksaccording to the invention, by executing machine-readable software codeor firmware code that defines the particular methods embodied by theinvention. The software code or firmware code may be developed indifferent programming languages and different formats or styles. Thesoftware code may also be compiled for different target platforms.However, different code formats, styles and languages of software codesand other means of configuring code to perform the tasks in accordancewith the invention will not depart from the spirit and scope of theinvention.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described examples areto be considered in all respects only as illustrative and notrestrictive. The scope of the invention is therefore, indicated by theappended claims rather than by the foregoing description. All changeswhich come within the meaning and range of equivalency of the claims areto be embraced within their scope.

The invention claimed is:
 1. A method of depth decoding using depthmodelling mode 1 (DMM1) for a depth block in a three-dimensional (3D) ormulti-view video coding system, the method comprising: receiving a videobitstream including compressed data for a depth block; determining, fromthe video bitstream, a reduced wedgelet pattern table including at leastone size-reduced wedgelet pattern or at least one omitted wedgeletpattern in at least one wedgelet direction category, wherein at leastone non-corner adjacent-edge sample for adjacent-edge partition or atleast one opposite-edge sample for opposite-edge partition is excludedfrom one or more starting positions or from one or more endingpositions, and said at least one size-reduced wedgelet pattern isgenerated according to said one or more starting positions and said oneor more ending positions; and decoding, from the compressed data, thedepth block according to DMM1 mode using the reduced wedgelet patterntable.
 2. The method of claim 1, wherein for the adjacent-edgepartition, said one or more starting positions correspond to evennon-corner adjacent-edge samples in a first adjacent edge and said oneor more ending positions correspond to even non-corner adjacent-edgesamples in a second adjacent edge.
 3. The method of claim 2, whereinsaid even non-corner adjacent-edge samples in the first adjacent edgecorrespond to first selected adjacent-edge samples in the first adjacentedge having first even sample distances from a corner sample joining thefirst adjacent edge and the second adjacent edge, and wherein said evennon-corner adjacent-edge samples in the second adjacent edge correspondto second selected adjacent-edge samples in the second adjacent edgehaving second even sample distances from the corner sample joining thefirst adjacent edge and the second adjacent edge.
 4. The method of claim1, wherein for the opposite-edge partition, said one or more startingpositions correspond to even opposite-edge samples in a first oppositeedge and said one or more ending positions include all opposite-edgesamples in a second opposite edge.
 5. The method of claim 4, whereinsaid even opposite-edge samples in the first opposite edge correspond toselected opposite-edge samples in the first opposite edge having evensample distances from a corner sample in the first opposite edge.
 6. Themethod of claim 1, wherein said decoding the depth block according toDMM1 mode using the reduced wedgelet pattern table including said atleast one size-reduced wedgelet pattern is applied to the depth blockonly when the depth block corresponds to a prediction unit with a blocksize equal to or larger than 16×16.
 7. The method of claim 1, whereinthe depth block corresponds to a prediction unit (PU).
 8. The method ofclaim 1, wherein the reduced wedgelet pattern table comprises at leastone size-reduced wedgelet pattern in each wedgelet direction category.9. The method of claim 1, wherein said one or more starting positions orsaid one or more ending positions correspond to every k-th non-corneradjacent-edge samples with phase t, wherein k is a positive integer andt is a non-negative integer smaller than k.
 10. The method of claim 1,wherein said at least one non-corner adjacent-edge sample for theadjacent-edge partition or said at least one opposite-edge sample forthe opposite-edge partition excluded from said one or more startingpositions or from said one or more ending positions depend on a blocksize of the depth block or a wedgelet direction category.
 11. The methodof claim 10, wherein said at least one non-corner adjacent-edge samplefor the adjacent-edge partition or said at least one opposite-edgesample for the opposite-edge partition is excluded from said one or morestarting positions or from said one or more ending positions only forthe block size of the depth block equal to or larger than a threshold.12. The method of claim 1, wherein the reduced wedgelet pattern tableincludes said at least one omitted wedgelet pattern in said at least onewedgelet direction category only for a block size of the depth blockequal to or larger than a threshold.
 13. The method of claim 1, whereinthe reduced wedgelet pattern table includes said at least one omittedwedgelet pattern in said at least one wedgelet direction category onlyfor a block size of the depth block smaller than a threshold.
 14. Themethod of claim 1, wherein one reduced wedgelet pattern table for acurrent depth block is used as a shared wedgelet pattern table byanother depth block having a different block size from the current depthblock.
 15. The method of claim 1, wherein a table size of the reducedwedgelet pattern table is pre-defined to a fixed value for each blocksize of the depth block, and a required table size associated with anumber of wedgelet candidates is no larger than the fixed value for eachblock size of the depth block.